The invention finds particular application in conjunction with almonds and will be described with particular reference thereto.

However, it is to be appreciated, the invention will also find application in conjunction with other types of nuts, seeds, dehydrated fruits, and other agricultural products.

To promote the growth of agricultural products, fertilizer is typically added to the soil. Manure, a commonly used fertilizer, can carry human pathogens, such as Salmonella, E-coli, and Listeria. When food items come into contact with the soil during harvesting, or with equipment that has contacted the soil, the food items can pick up the human pathogens on their surface. As the harvested food items are gathered together, the pathogens can be passed from surface to surface by direct contact.

When harvesting almonds, for example, it is common to shake the trees dropping the almonds (in their shells and husks) to the ground. The almonds are then collected from the ground. In a first operation, the husks are removed from the almonds, leaving the almonds in their shells. Some almonds are sold in their shells, and others are deshelled prior to packaging. The removed husks would be expected to be the carriers of any human pathogens picked up from the soil. Even after husking, the shell provides a pathogen impermeable package

for the nutmeat. Conventional, mechanical shelling operations raise a significant amount of dust, sending dust-sized portions of the shell and any pathogens which might be thereon airborne.

Subsequently, the shelled nutmeats undergo various sorting operations. Some of the nutmeats are cooked, which would also be expected to kill any surface pathogens. Other nutmeats are packaged and sold raw. Although the chances of human pathogens being present on the packaged nutmeats might appear relatively remote, there have been recent recalls of almonds for Salmonella contamination.

One solution to the contamination problem is found in the present assignee's U. S. Patent Nos. 5,460, 845 and 5,535, 667. These patents describe a batch process in which almonds and other food items are exposed to hydrogen peroxide vapor in a vacuum chamber for periods of about a half hour to one hour. These patents also describe limited kill rates at somewhat shorter periods of exposure at atmospheric pressure.

Although effective, such batch processing techniques are not readily compatible with modern processing plants in which each processing line processes about 10,000 kilograms of food product per hour or more.

The present invention overcomes the above-referenced problems and others.

Summary of the Invention In accordance with one aspect of the present invention, a method of sanitizing human pathogens from surfaces of agricultural food products is provided. The food products are moved continuously on a porous belt. While the food products are moving along the belt, they are treated with a gaseous oxidizing agent at atmospheric pressure for a sufficient duration to kill human pathogens.

In accordance with another aspect of the present invention, an apparatus for sanitizing human pathogens from surfaces of agricultural food products is provided. A porous belt continuously conveys the food products into, through, and out of a food chamber. A means is provided for supplying a gaseous oxidizing agent to the chamber to treat the food

products. The chamber has a length relative to a speed of the mesh belt such that the food products remain in the chamber for a sufficient duration to kill human pathogens.

One advantage of the present invention resides in its speed.

Another advantage of the present invention is that it provides a flow-through sanitization system which can process food products at the same rate that they are moving along conventional processing assembly lines.

Another advantage is that the present invention kills human pathogens in 30 seconds or less.

Another advantage of the present invention is that it does not alter the taste of the food products.

Another advantage of the present invention is that it does not alter the value of almonds by changing the appearance of the brown skin or pellicle.

Still further advantages and benefits of the present invention will become apparent to those of ordinary skill in the art upon reading and understanding the following detailed description of the preferred embodiments.

Brief Description of the Drawinas The invention may take form in various components and arrangements of components, and in various steps and arrangements of steps. The drawings are only for purposes of illustrating preferred embodiments and are not be construed as limiting the invention.

FIGURE 1 is a diagrammatic illustration of a husking and shelling line in accordance with the present invention; FIGURE 2 is a diagrammatic illustration of a processing line for shelled nuts or other foods products in accordance with the present invention; FIGURE 3 is a detailed illustration of a preferred treatment chamber of FIGURES 1 and 2; FIGURE 4 illustrates bacterial concentration reduction in 15 second intervals; FIGURE 5 illustrates bacterial concentration reduction relative to a 105 control.

Detailed Description of the Preferred Embodiments At harvest time, almonds or other shelled food products are received in bulk at a dehusking and deshelling facility 10. The bulk almonds are emptied into a large hopper or other supply 12 from which almonds or other foods products are supplied to a husk removing machine 14. The husk removing machine discharges almonds in the shell at one output 16 and outputs the husks through a second output 18. The husks are removed from the facility and sold for other agricultural uses, such as additives to livestock feed. The almonds in the shell from the outlet 16 are conveyed to a first sanitization chamber 20 on a mesh conveyor belt 22.

The sanitization chamber 20 exposes the almonds in the shell to a gaseous oxidizing agent such as ozone, vaporized liquid oxidants, condensed oxidants, plasma, or the like and combinations thereof. In the preferred embodiment, the gaseous oxidizing agent is in the form of hydrogen peroxide vapor in a concentration of about 1.8 milligrams per liter of air or greater. More specifically to the preferred embodiment, liquid hydrogen peroxide from a liquid hydrogen peroxide source 24 is fed to a vaporizer 26 at a controlled rate. In some cases, it is advantageous if air is dried by a dryer 28 and blown by a blower 30 into the sanitization chamber 20.

An exhaust blower 32 draws peroxide vapor and water vapor from the sanitization chamber and exhausts them to the atmosphere. The exhaust blower 32, preferably, is operated at a speed relative to the feed blower 30 such that the treatment chamber is maintained at a negative pressure relative to atmosphere so that the vapor hydrogen peroxide does not escape into the working atmosphere. Because the almonds are still in the shell and protected, the treatment chamber 20 can tumble or agitate the almonds, use a stronger concentration of the gaseous oxidizing agent, and can even use oxidizing agents which would leave a residue or adversely affect taste. Preferably, a microbe impermeable barrier wall 34 is maintained across the hulling and shelling facility 10 with one side of the wall being

on the input to the treatment chamber 20 and the other side on the output. The chamber 20 has a length, relative to the conveyor belt speed, such that the almonds take 15-30 seconds to traverse the chamber.

From the sanitization chamber 20, the almonds are conveyed to a shelling machine 40 which removes the shells from the almonds. The nutmeats are discharged from a first outlet 42 and the shell fragments are discharged through a second outlet 44. Optionally or alternately, a second sanitizing chamber 20'of the structure described above is disposed after the nutmeat outlet 42. A packaging machine 46 packages the shelled almonds in relatively large containers, such as 50 lb bags, drums, pallet sized containers, and the like. Preferably, the bulk containers are sealed against airborne pathogens. By sanitizing the portion of the husking and shelling facility 10 which is downstream from the barrier wall prior to the receipt of almonds and by sanitizing all of the almonds in the shell entering the area, all of the packaged nutmeats should be free of human pathogens. Because the husking and shelling operations are commonly performed only around harvest time and the packaging and production lines run year-round, the containers of shelled almonds are typically stored anywhere from a few hours until the next harvest season.

With reference to FIGURE 2, at a packaging facility 50, the shelled nutmeats are received in a hopper 52 or other supply and fed at a controlled rate onto a mesh conveyer 54 preferably in a layer one nut thick. A barrier wall 56 surrounds the hopper 52 and isolates the area of the hopper from the remainder of the production facility.

A sanitization or treatment chamber 60 penetrates the barrier wall 56 such that its inlet receives untreated nuts on the conveyer 54 and its outlet discharges sanitized nuts or other food products on the conveyor 54 which continues downstream. The use of the barrier wall and treatment chamber 60 at the entrance to the processing facility assures that only treated nuts or food products enter the facility. This prevents cross contamination downstream. For example, nuts which are

roasted go through a heating process which would normally kill the human pathogens. However, if the roasted nuts should come in contact with a contaminated, not yet roasted nut, or even a worker who had come in contact with a not yet roasted nut, human pathogens can be transferred to the previously sanitized roasted nuts. When every nut in the facility is sanitized, the chances of cross-contamination are minimized.

The treatment chamber 60, like the treatment chamber 20, includes a source 62 of a gaseous oxidizing agent, such as an ozone source, other vapor sterilant source, or a plasma source. Again, a source of liquid hydrogen peroxide of about 35% concentration and a vaporizer are preferred. A blower 64 supplies the gaseous oxidizing agent into the treatment chamber 60. The gaseous oxidizing agent, after moving among the food product, passes to an exhaust where a blower 66 exits the gas to atmosphere. Again, the relative speed of blowers 64 and 66 are preferably such that a slight negative pressure is maintained in the treatment chamber. More preferably, air curtains 68 are provided at the inlet and the outlet. The air curtains prevent the gaseous sanitizing agent from escaping from the chamber into the surrounding processing facilities and prevent contaminants from the surrounding facilities which could alter the sanitization process from entering the chamber. For example, if excess humidity from the production facility entered the treatment chamber, the water vapor could dilute the treatment gas or could alter the vapor pressure in the chamber, permitting condensation to occur.

The treatment chamber 60 has a length which is calculated such that at the normal movement speed of the conveyor belt 54, the food products dwell in the chamber for a prescribed treatment time, preferably 15-30 seconds. The flow of the gaseous oxidizing vapor through the chamber is sufficiently vigorous that the food products vibrate on the mesh conveyor belt, changing their points of contact and permitting all portions of the surface to be treated with the oxidizing vapor. Yet, the gaseous oxidizing agent flow is preferably not so vigorous that the food products are agitated to the point

that they can become scarred or otherwise loose cosmetic appeal, hence value.

The sanitized almonds or other food products are passed to downstream processing equipment 70. This equipment includes sorting stations for sorting the food products by quality, e. g. , broken versus unbroken nuts, nuts with whole unscarred pellicles versus nuts without, and the like. The sorted nuts are conveyed to various processing lines. For example, some pass to roasting stations where they are roasted, salting stations where salt or other spices are added, and the like as is conventional in the food processing arts. Finally, a packaging machine 72 packages metered amounts of the processed food product into appropriate consumer packages.

With reference to FIGURE 3, the sanitizing systems 20 and 60 preferably include an inlet duct 80 which supplies air to a housing 82 which houses an appropriate dryer for the incoming air, liquid peroxide supply, vaporizer, and blower.

Vapor output tubes 84 supply the generated vapor to distributed portions of a lower manifold 86. The vapor is moved upward through the mesh conveyor belt 54 into an upper manifold 88.

Vapor from the upper manifold 88 is pulled by a blower through a catalytic destroyer which converts hydrogen peroxide vapor to water vapor and discharges the water vapor through a discharge duct 92.

With reference to FIGURE 4, sample almonds were inoculated with 3. 7x108 inoculum of salmonella bacteria to achieve an initial bacterial concentration of about 106. These almonds were treated with 1.8 milligram/liter concentration of hydrogen peroxide vapor at 33-34 C. FIGURE 4 illustrates the log reduction at 15 second intervals. It will be seen that 15 seconds produces about a 3 log reduction. Similarly, FIGURE 5 shows the relative reduction of a test sample 100 at 5 second intervals from a 105 initial bacterial concentration, relative to a control 102 that was not subject to the hydrogen peroxide vapor. Again, a 3 log reduction was achieved in 15 seconds.

Although tests were conducted at 5 logs, naturally infected

almonds are more apt to have an initial bacterial count in the order of 102-103 Salmonella.

The oxidizing agent treatment is preferably conducted at temperatures below 40 C. Higher temperatures tend to cause cooking of oil in the nuts and other food products, altering flavor. Hydrogen peroxide vapor is also preferred. Exposure to concentrations of 1.8 mg/liter for periods of many minutes have been shown to have no adverse organoleptic effect on the treated product. Further, hydrogen peroxide vapor does not require an aeration zone. Although 15 seconds provides sanitization of human pathogens, longer exposure times can also be used to kill spores and achieve a higher level of kill. Such higher levels of kill would improve not only safety, but also the safe shelf time for the products.

Although described with particular reference to almonds in the preferred embodiment, it is to be appreciated that similar concerns and treatment parameters are also effective on a wide variety of nuts and grains, seeds, and spices. The processes are also amenable to dehydrated and dried vegetables and fruits.